Higher mammals - cats, dogs, horses, etc - recognise human friends. So do some birds. One reason they’re popular pets. But I’ve never heard this of other groups. Which other groups recognise friends? I really don’t think I could trust any shark or snake, for instance.
Various mutualistic animals recognize each other-remoras and sharks and other large fish, for example. That little bird which cleans a croc’s teeth. Tons of examples.
Yes there are many animals who have cross species symbiotic relationships. I saw a case once where a female maine-coon cat raised a brood of Opossum. I’ll look for some pics.
Many bird species (perhaps all?) recognise each other- most of them are monogamous, either for a breeding season or for life, which implies that they are able to distinguish between other individuals. I don’t think most birds could distinguish between two humans, although I know my in-laws’ budgies do.
Sheep apparently are very good at recognizing individual faces http://news.nationalgeographic.com/news/2001/11/1107_TVsheep.html
Yes, I covered mammals and birds in my OP. Cats, dogs, etc will recognise and respond not only to ‘their human’ but also to other humans with whom they’ve had friendly relations. For instance there was a local ginger cat who loved my attention, but he wasn’t mine. Equally, another cat will take one look at me and run away. Each cat recognised me as me rather than me as a human. Are there non-mammals and non-avians that can do this?
The alligators at gaterland zoohave been conditioned by some of the trainers there, and some of the trainers even say that certain gaters “know” them by sight and wouldn’t act aggressively towards certain trainers.
Just an observation - any animal that usually exists in a group that contains a hierarchy (packs, pods, herds, etc) would probably possess the ability to recognize and respond to individuals and could possibly implement that trait with individuals of other species.
I bet a saltwater crocodile can distinguish between flavors of humans.
I once had an Oscar fish that could distinguish me from other people. It would come up in anticipation of being fed by me but no one else.
There are a few monogamous lizards. In some cases the pairs can split up months, possibly years, at a time and still recognise each other when they meet again. So it’s certainly not restricted to warm blooded critters.